Impacts of urbanization on Austin’s water resources Austin, 1981, Shoal Creek near 12 th Street Area inundated by 1981 flood in Austin Wastewater leak Raymond Slade, Jr. Registered Professional Hydrologist

Presentation organization Urban impacts on floods and runoff Bank erosion due to urbanization Urban streamflow quality degradation and sources Barton Springs water quality trends Construction impacts on water resources Use and impacts of Best Management Practices Emerging contaminants in Source Drinking Water Sediment quality in Lady Bird Lake PAH’s Cost to mitigate urban water resource problems Information on stormwater management

Runoff increased by impervious cover Urbanization increases flood peaks for all floods, causing greater losses of life and property. A US Geological Survey study in the Central Texas area documents that a 2-year flood peak (that with a 50% chance of occurring each year) increases by 99% when a rural basin is fully urbanized. Also, a 100-year flood peak increases by 73% when a basin is fully urbanized. This conceptual hydrograph shows peaks in an urban basin to be higher than those in a natural basin Also, urban peaks occur sooner after stormsthan rural peaks, thus less time is available for remedial actions or evacuation from severe floods. Also, urban peaks occur sooner after storms than rural peaks, thus less time is available for remedial actions or evacuation from severe floods. Urban impacts on floods and runoff

Relations between impervious cover and runoff Runoff as ratio of rainfall Impervious cover as ratio of total area Runoff data from Austin streamflow gages shows runoff from rural areas to be about.05 or 5% of rainfall while runoff is about 40% of rainfall when impervious ground cover is 50% Data from City of Austin

Urbanization causes increases in the number of bankfull flows. A watershed with 25% impervious surfaces is subjected about once every five years to a peak flow equivalent to the 100-year storm under undeveloped conditions. More frequent floods cause bank erosion as shown in photos of streams in developed basins in the Austin area. Erosion threatens property and dwellings and increases stream bed sediment and sediment in streamflow. Bear Creek Shoal Creek Fort Branch Boggy Creek Bank Erosion due to urbanization

Bank Erosion (cont.) E. Bouldin Creek Walnut Creek Tannehill Branch Shoal Creek Little Walnut Creek

Urban streamflow quality degradation and sources Data from U.S. Geological Survey stream gages in Austin area Data from Veenhuis and Slade (1990)

Relation of impervious cover (as ratio of total ground cover) to mean values of water quality constituents for gaged Austin streams Dissolved phosphorus (mg/L) Copper (micrograms per liter) Ammonia nitrogen (mg/L) Lead (micrograms per liter) Data from City of Austin

Point sources of urban runoff Discharges from businesses, industry, mining Permitted – sewage & industry effluent discharges (liquid or solid) Non-permitted – leaking storage tanks, spills, dumps Non-permitted – leaking storage tanks, spills, dumps

Non-Point Sources of urban runoff Urban development construction, sewage, autos, parking- lots, pesticides, fertilizers, industry, animals Urban development – construction, sewage, autos, parking- lots, pesticides, fertilizers, industry, animals

Barton Springs water quality trends

In 1980 decade, sediment in runoff from the construction of Barton Creek Square Mall entered Barton Creek and discharged from Barton Springs within hours of rainfall. The sediment concentrations at the Springs were so great that the springs pool had to be closed during such events. Sediment in water sample from Barton Springs The mall covers about ¼ square mile and Barton Springs flow comes from about 350 square miles yet construction sediment from the mall was so great that visibility in the pool approached zero. Measure of turbidity from sediment during storm Barton Springs

Barton Creek upstream from Barton Springs Algae from leaking sewer line

Another example of leaking sewer line Tannehill Branch, Austin

Total nitrate + nitrate all % Total dissolved solids all % From “Is Barton Springs polluted?” Slade (2003)

Construction impacts on water resources Construction typically involves removal of vegetation for work access roads and for building of structures, parking lots, and utility lines. Vegetation attenuates much of the contaminants in overland flow, thus its removal causes water-quality degradation of receiving streams. Also, many tons of loose sediment are created during this process— sediment which washes into receiving streams, reservoirs, and aquifers, often prohibiting the use of such water and causing loss of biological life. Construction sediment can represent the greatest threat to urban aquatic resources.

Along with sediment, typical construction site pollutants include fluids from construction equipment, adhesives, paints, cleaners, masonry, cement, fertilizers, pesticides, and wastes from electrical, plumbing, heating, and air conditioning installations. Along with sediment, typical construction site pollutants include fluids from construction equipment, adhesives, paints, cleaners, masonry, cement, fertilizers, pesticides, and wastes from electrical, plumbing, heating, and air conditioning installations. Bee Cave Galleria in Barton Creek basin Pesticide washed into creek from improperly stored bags Dead fish in receiving stream Example of pesticides in runoff from Bee Cave Galleria development in the Barton Creek basin.

Effect of erosion and sediment controls on suspended sediment concentrations Construction site condition Data from Piedmont, Ca. A BMP is a “Best Management Practice” Use and impacts of Best Management Practices

Construction controls most used in Texas Silt fences which often fail during large storms Sediment from construction

April 2007 photograph of sediment-saturated runoff from the AMD construction site, fouling stream waters with mud that was supposed to be stopped by a silt fence

Available Sediment Controls Construction plans and controls used throughout the U.S. 1. Minimize Clearing 2.a. Protect Waterways Buffers and special crossings for waterways Buffers and special crossings for waterways 2.b. Stabilize Drainageways Checkdams, sod, erosion control blankets, rip rap Checkdams, sod, erosion control blankets, rip rap 3. Phase Construction 4. Rapid Soil Stabilization hydroseed, mulch, erosion control blankets hydroseed, mulch, erosion control blankets 5. Protect Steep Slopes 6. Perimeter Controls Earth dikes, diversions, silt fences, stabilize construction entrance Earth dikes, diversions, silt fences, stabilize construction entrance 7. Employ Advance Settling Devices sediment traps & sediment basins sediment traps & sediment basins 8. Certified Contractors Implement Plan 9. Adjust Plan as Field Conditions change 10. Assess and Revise Practices After Storms Repair damage, modify practices, reinforce, cleanout Repair damage, modify practices, reinforce, cleanout Note: Most of these practices are not commonly used in Texas

Available sediment construction controls Slope protection hay mulching Hydroseeding operation Hay mulch ground cover Use of mats to minimize erosion

Available sediment construction controls (cont.) Sedimentation basin with standpipe Checkdams Berm dividing multi-cell sedimentation basin

Available sediment construction controls (cont.) Swale to divert runoff around construction site in non-erosive manner Mats and hay to stabilize channel Rock to stabilize channel

Emerging contaminants in Source Drinking Water Pharmaceuticals - Excreted into waste water - Antibiotics, hormones, analgesics Other waste-water indicators - Flame retardants, surfactants, fragrances Planned for future sampling

During 2001, a network of 25 ground-water and 49 surface-water sources of public drinking water supply in 25 states and Puerto Rico were sampled and analyzed for 124 emerging contaminants. Surface water site Groundwater site From USGS

Findings At least one emerging contaminant (including some compounds such as plant and animal steroids) was detected in about 96% of the samples. A median of 4 compounds were detected per site indicating that the targeted chemicals generally occur in mixtures (commonly near detection levels) in the environment and likely originate from a variety of animal and human uses and waste sources. From USGS

USGS Program Reconstructed trends gov/fs/fs /fs htm Sediment analyses from core samples of Lady Bird Lake Sediment quality in Lady Bird Lake

Sediment analyses from core samples of Lady Bird Lake PCBs (Polychlorinated biphenyls ) are a group of manufactured organic chemicals that contain 209 individual chlorinated chemicals (known as congeners). PCBs are a probable human carcinogen. PAHs (polycyclic aromatic hydrocarbons), a group member of organic compounds formed during incomplete combustion of organic matter, are in fuels such as gasoline, coal, and fuel oil. PAHs generally are toxic to humans and may be a human carcinogen

PAH’s PAH from Parking lot sealants represent a newly discovered major source of urban contamination. PAH (polycyclic aromatic hydrocarbons), a group member of organic compounds formed during incomplete combustion of organic matter, are in fuels such as gasoline, coal, and fuel oil. Sealants reapplied every few years. About 600,000 gallons of sealant are applied annually in Austin. Levels of PAH sampled from parking lots coal-tar- emulsion- sealed asphalt- emulsion- sealed unsealed asphalt or concrete From USGS

City of Austin Watershed Protection Master Plan Phase Management of urban runoff problems runoff problems Cost to mitigate urban water resource problems Assess technical information to identify erosion, flood and water quality problems Prioritize problem areas Identify and evaluate solutions Integrate solutions across missions (erosion, flood, water quality Develop and implement solution

Information on stormwater management The Center for Watershed Protection ( and National Stormwater center ( have information regarding the following subjects Why watersheds Why watersheds Impacts of urbanization Impacts of urbanization Better site design Better site design Tools for watershed protection (next slide) Tools for watershed protection (next slide) Stormwater Best Management Practices Stormwater Best Management Practices

Tools for watershed protection Center for Watershed Protection (CWP), “Economics of Watershed Protection” Article 30 Watershed Protection Techniques 2(4) pp 469 – 481. Center for Watershed Protection, Elliott, MD. 8 tools (CWP, 2000, fig 1, p. 161)9 tools (CWP, 2000, table 3 p. 16)